Energy drinks are soft drinks, generally carbonated, composed of different ingredients such as caffeine, taurine, glucuronolactone, carbohydrates and vitamins with different rates of absorption to which the proposed effects of these beverages are attributed [1-3]. Furthermore, depending on the brand, these solid drinks have other ingredients such as amino acids, minerals and vegetable extracts, together with acidulants, preservatives, flavorings and colorings. These types of products have gained popularity worldwide since the 1990s, increasing exponentially the consumption among adolescents, athletes, and even senior citizens . Manufacturers of these products promote their consumption with statements offering a variety of benefits among which increased physical performance, improved reaction rate, increased attention, higher concentration, improved emotional state and weight loss are included . These are desirable characteristics for anyone, especially for active individuals. The interaction of the major bioactive compounds has been proposed as responsible for the alleged effects of these products; however, such statements have not been well studied and are not fully supported. Furthermore, there are contradictory results on the issue. Some studies attribute the alleged effects in improving the state of concentration and physical endurance to the combination of the compounds that make up these products [5,6]. Other studies point out that is very likely that most of the observed effects after consumption of these drinks are mainly produced by caffeine [7-9]. On the contrary, other studies have found no increase in the performance after consumption of these collagen peptide drinks .
Currently, many people seek benefits for their physical and mental health situation that has led them to use these types of meal replacement drink; nonetheless, despite an increased consumption by the general population, there is a lack of knowledge about the physiological effects of the compounds used in the formulations, the level of security in their consumption and their position within food standards. This is probably because there are few well-designed studies that provide accurate and conclusive findings on the subject.
Therefore, in this study we evaluated the efficacy and safety of energy drink consumption in a randomized, controlled, double-blinded, crossover trial and thus we were able to assess the direct involvement of caffeine and taurine, as major bioactive compounds of energy drinks, on physical and cognitive condition in young adults.
A sample of 9 or 13 subjects was calculated in order to find differences in cognitive or physical tests. This was done by using PRIMER software 3.02 (PRIMER-E Ltd, United Kingdom), after establishing a confidence level of 95% and a power of 80%. Nonetheless, 14 volunteered male soldiers, members of the National Army of Colombia Seventh Division, were included in the study. No cigarette smokers or users of psychoactive substances, or subjects under any medication (e.g. beta blockers) were included. People who consumed more than 600 ml of coffee or more than 5 units of colas per day were excluded .
All participants underwent a complete physical examination and an electrocardiogram to determine their physical and mental conditions and all were diagnosed as healthy. In addition, they all signed the informed consent before the physical and cognitive tests. The procedures performed were endorsed and approved by the Indeportes Antioquia Research Committee and the National Army Research Committee in order to provide protection to the study participants.
This research used a double-blind, placebo controlled, randomized, crossover design, in which each participant visited six times the Exercise Physiology Laboratory from Indeportes Antioquia, in Medellín, Colombia, at 1540 m above sea level. Three fitness tests and two cognitive condition tests were applied in each visit. All evaluation sessions were separated between 48 or 72 hours and three subjects were evaluated per day. In the first session the subjects performed the tests, without drink consumption, to become familiar with their development. Testing was always conducted at the same time (2 pm-5 pm) in an environment with controlled temperature and humidity of 25°C and 60%, respectively. A training specialist and a psychologist with extensive experience in sports fields were responsible for measuring all variables.
Participants maintained their regular food intake, workplaces and recreational activities during study participation, but did not train at high intensity eight hours before the tests, did not eat heavy meals two hours before the tests and avoided caffeine consumption during the day of evaluation. Since the participants were soldiers, they had a very controlled schedule regarding food and exercise every day. So we are sure that during the day of evaluation the variation in these variables was kept to the minimum. All subjects used appropriate clothing for physical exercise.